Hello Mel,

The error is shown because there is some post or tag or category which has a invalid author id. I believe the user account with the id of 14 has been deleted from the site and it looks like the EasyDiscuss user plugin isn't installed on the site hence the orphan scripts isn't working. Can you download and install EasyDiscuss user plugin and see how it goes.

If this issue is still persist, perhaps you can provide us with backend access, so that we are able to assist you on this issue.
Please be advise.
Thanks.